Friday, February 24, 2017

The number of cities in the world depends on how you count
but it’s a big number. Brilliant Maps
says more than 4000 cities have more than 100,000 inhabitants. The UN
says 1692 cities have more than 300,000 inhabitants and 512 cities have at
least 1,000,000 inhabitants (totalling 23% of the World’s population). And,
hey, www.answers.com helpfully narrows the
number of cities and towns down to somewhere between 600,000 and (apparently) 4,784,754,000.
No matter how you slice it, I am certain there are 2,000 major urban areas with
lots of people in them.

Cities change everything for the organisms that live in
them. Temperature changes. Noise changes. Available habitat changes. Prey
changes. Predators change. Food changes. Pollution. Eutrophication. Invasion
species. For years, the temptation was simply to write these areas off from the
perspective of biodiversity and nature; but – over many years – a shift has occurred
to establish a vigorous field of “urban ecology”. The idea is that cities are
ecosystems too and we should manage them and their biodiversity as such. And
where ecology goes, evolution follows. That is, any sort of environmental
change is expected to impose selection on the organisms that remain in that
environment, which should lead to evolutionary adaptation to urban
environments. This post is about how urbanization dramatically shapes the evolution
of many species. I might have called it “Darwin Comes To Town” but Menno Schlithuizen’s
forthcoming book has already appropriated that wonderful title.

The past few decades saw a smattering of studies
demonstrating evolution in response to urban environments. Byrne et al. (1999) showed that a new form (species?) of mosquitoes had evolved in the London Underground. Cheptou et al. (2008) showed that
plants evolved reduced dispersal in cities because dispersers were likely to
end up in the in hospitable “concrete matrix.” Following from these earlier, somewhat sparse demonstrations,
studies of urban evolution have really heated up recently: cool new papers are
coming out, books are being written, grants are under review, symposia are
being organized,
and working groups are being convened. Inspired by this recent enthusiasm, I
want to highlight some of my own work in this area, some of the exciting new work
that has come out this year, and some attempts to tie it altogether through
meta-analysis.

Darwin's finches of multiple species near Puerto Ayorra pigging out on rice provided by humans.

My own foray into urban evolution started with coincidental
discoveries in Darwin’s finches of Galapagos. Up to the 1970s, medium ground
finches (Geospiza fortis) at Academy Bay, beside the
small town of Puerto Ayora on Santa Cruz Island, were bimodal in beak size: many
large or small birds with relatively few intermediates. By the time we started
working there in the 2000s, Puerto Ayora had grown dramatically, and the
collection of new beak size data did not reveal the same bimodality as in the
past. Yet at the same time, we uncovered bimodality at a site (El Garrapatero) well removed from
the town where finches were not exposed to urban conditions. Compiling data
from 1964 to 2005, we confirmed
that beak size bimodality was lost the finches living in and around Puerto
Ayora coincident with the dramatic human population increase. We then showed in
later work that this collapse of diversity was associated with a degradation
of the diet differences that normally differentiate the species. In short, all
the finches are now feeding on human foods, which has removed the selection
pressures formerly favoring diversification in this group. Indeed, additional
work we currently have in review shows that urban finches are actively
attracted to humans and their foods, whereas finches outside of the city are
not.

Acorn ant colonies are entirely contained within acorns,
which is pretty darn cool – and makes for a wonderful experimental system. One
can pick up an acorn and move it to a new site, or to the lab, and thereby test
for thermal tolerances and local adaptation. And – conveniently for the
question at hand – oak trees producing lots of acorns are found both inside and
outside cities. Sarah Diamond and colleagues tested whether urban acorn ants
had different temperature tolerances than rural ants. Consistent with the “urban
heat island” effect (temperatures are higher inside cities than outside), the
authors found
that city acorn ants had higher thermal tolerances, and that this difference could
be attributed to a complementary combination of plasticity (warmer rearing
temperatures increased thermal tolerance) and genetic differences (city ants
had higher tolerances for a given rearing temperature). But the temperature
effects of cities might not always be so straightforward.

One of the most ubiquitous plants in urban environments is
clover – as a kid, I spent many hours searching for 4-leafed versions. Clover
is also abundant outside cities, and so might be a good model for understanding
how evolution proceeds in response to urban conditions. Marc Johnson, Ken
Thompson, and colleagues hypothesized that the urban heat island effect should lead
to the evolution of reduced freeze tolerance in clover, which is controlled by
a known genetic polymorphism for hydrogen cynanide. Surprisingly, they found
exactly the opposite – freeze tolerance genotypes were more common inside
Toronto than outside. The same result was obtained for New York and for Boston,
whereas no pattern was evident for Montreal. After a long trip down the rabbit hole,
the authors showed
that, because snow cover is less common in cities than without, some cities are
actually “urban cold islands” in winter that favor the evolution increased –
rather than decreased – cold tolerance in plants. (Montreal has so much snow
both in and out of the city than it doesn’t matter.)

The use of multiple urban-nonurban gradients, as above,
allows greater insight than only a single gradient. Also this year, Liam
Revell, Kristin Winchell, and their collaborators studied Anolis lizards on Puerto Rico, comparing those in three cities to
those just outside the cities. In forests, these lizards are commonly found on
branches that can be quite narrow, whereas in cities they tend to occur on the
much broader substrates of walls. Previous work showed that hindlimb length
tends to evolve according to substrate size – being longer on broader
substrates. That was just what the authors found
here: city lizards have longer legs and a common-garden rearing environment
confirmed that at least some of this difference was genetic.

The above examples are just a few studies from this year.
Many other studies are also demonstrating trait responses to urbanization,
although, in some cases, it isn’t yet clear if the change is genetically based.
City birds sing different songs,
appear smarter,
have different behaviors and stress responses, sometimes have different clutch sizes, and so on. City mice differ in key genes that might reflect adaptation, Daphnia evolve to be smaller in urban ponds, and so on. These wonderful examples of phenotypic changes (at least some evolutionary)
in urban environments raise the question: are they exceptional? Humans
influence evolution in all sorts of contexts apart from cities
(hunting/harvesting, fragmentation, climate change, pollution, eutrophication, invasive
species, etc.), as we recently reviewed in a special issue
of PTRSB. Are urban environments any different, such as by driving faster rates
of change than in other contexts?

Marina Alberti
has led the recent charge in reviewing work on urban evolution and contacted me
with an idea to use our database of rates of phenotypic change to
quantitatively ask if changes were greater in cities than in “natural” or other
human-disturbance contexts. The same database had previously been used to show
that – among other things – human disturbances accelerated
rates of change, that the most dramatic effects were evident when humans acted as predators,
but that evolution was not exceptionally rapid in the context of
invasive species. Georeferencing all the observations in this database and
linking them to urbanization estimates, the study – a collaboration among many
people – showed
that adding information on urbanization substantially improved the ability to
predict rates of change – a number of which are confirmed to be genetically
based. I speculate that the main reason is that urbanization is associated with
many forms of environmental change occurring all together (a subset are listed
at the outset of this post), which should impose particularly strong and
diverse selection on the organisms that persist.

Locations of rate data used in our analysis.

The next time you walk through a city, take a look past the
steel, glass, and concrete, to see the plants and animals that live there. (And,
of course, to not see all the microbes.) Each of these organisms is experiencing
selective pressures that simply didn’t exist in most places until relatively
recently. Selection is the engine of evolution and – indeed – many of these
organisms have evolved to better suite them for urban conditions. Indeed, some
of those organisms might not exist in cities were it not for adaptive evolution
keeping pace with increasing urbanization.

Urban evolution is the new hot Broadway (and off-Broadway)
play in the evolutionary – and eco-evolutionary – cannon. See it now.----------------------------------------Here are some Darwin's finches pigging out in the Baltra Airport, Galapagos.

Saturday, February 11, 2017

Sabbaticals might seem a strange thing to students,
administrators, politicians, the general public, and – well – everyone who
doesn’t take them. A common perception is that professors who take a sabbatical
are “taking a year off” – and certainly that sometimes happens. As a result of
perceptions such as this, some countries don’t allow paid sabbaticals, some
states within countries don’t allow paid sabbaticals, and some particular
universities don’t allow paid sabbaticals. In many other cases, only partial support
is provided or the time between sabbaticals increases beyond the normal every-7th-year.
In this post, I make the case for fully paid sabbaticals every 7th
year as the greatest benefit to everyone.

7 years after starting to work on it, my book arrived in the mail today. Sat down to read and promptly fell asleep. pic.twitter.com/YP9VLWpuYC

About the above: I started my Eco-Evolutionary Dynamics book on my first sabbatical and finished it on my second sabbatical! Only sabbaticals made it possible. For more see https://storify.com/EcoEvoEvoEco/peoplewhofellasleepreadingmybook

Teaching (and service) improves

Most people who do not attend university – and even many people
at universities – think that what professors are for is teaching (and various
committee-style “services”). Certainly, most professors do a lot of teaching,
which is how most students know them. So, if the role of professors is to
teach, and they don’t teach on sabbatical, then they aren’t doing their job on
sabbatical – so they shouldn’t be paid. This logic is precisely why legislators
in some countries and states forbid paid sabbaticals. Professors have other
important jobs besides teaching and service – and those other jobs (research!)
benefit dramatically from sabbaticals. However, I first want to make the point that
even teaching benefits from sabbaticals. The main reason is that: “The
biggest thing for the professors is they get the chance to refresh themselves
and to escape. They come back … invigorated.”

Teaching the same course year after year after
year (or even different courses year after year after year) can whittle away at
enthusiasm and the motivation to make major improvements. A year away can
completely re-invigorate a professor’s motivation to teach, teach often, and
teach well. (Part of this motivation comes from the guilt a professor feels
when his/her colleagues have to teach those courses for a year.) From my own experience,
I definitely feel this benefit is critical. Just this fall – right after my
sabbatical – I taught three courses: my graduate class in Advanced Evolutionary
Ecology, an undergrad class in Evolution, and our Introductory Biology class. I
also took over coordination of the last of these and gave guest lectures in a
number of other classes. Teaching was exciting again – fun again – motivating again.
I wanted to do new things, exciting things, more things. This sort of excitement
and motivation really improves with a year away from teaching.

Importantly, classes rarely suffer from
sabbaticals in the sense that most of the classes are taught anyway – just by other
professors. Hence, the long-term benefit to teaching does not come with any major
short-term costs. Sabbaticals are good for teaching!

Research improves

The primary thing that many professors do is
research. In fact, research at many universities is what professors are supposed
to spend most of their time doing. This is critical. Universities are not just
about the transfer of information and ideas from experts (professors) to
trainees (students), they are just as much about the generation of new ideas and new knowledge. Moreover, this
generation of knowledge benefits the transfer of knowledge because students
respond much more strongly to professors who are speaking from their own
experience – and often injecting examples from their own work. And then
undergraduate (and graduate) students can become involved in the research and
thereby have real “hands-on” training. In my lectures, I specifically emphasize
research conducted by McGill undergraduates who were sitting in the same seats
as the current crop of students in the class. Research benefits teaching!

Sabbaticals have a HUGE effect on research
because they afford the time and motivation to learn new methods, write new
grants, publish that backlog of papers, do intensive field or lab work, etc.
Some professors travel to places where they can get training in new
technologies. Some professors travel to places where they can be close to their
field work, or their collaborators, or important infrastructure. Some
professors remain local and focus on publishing papers. On sabbatical,
professors have the time to think about science, do science, write science,
learn science. Sabbaticals are critically important for research success,
particularly “taking it to the next level.”

Apparently not everyone (or every study) finds
that average research productivity goes up after sabbaticals. This doesn’t mesh
with my experience. Some years ago, Keith Crandall was telling me a story about
how he was fighting to convince the administration of a university of the value of sabbaticals.
Among other things, he showed a graph of his publication rate in relation to
the timing of his sabbaticals. When preparing this post, I asked Keith about
graph and he was able to recreate it from Web Of Science – showing big jumps in
publication productivity with each sabbatical.

Keith: thanks for the idea and the graph!

I did the same calculations for
myself and found the same thing – big jumps in productivity with each
sabbatical. Beyond benefits accruing to the professor and the people influenced
by his/her research, universities are often ranked based largely on professor
research productivity – and these rankings can have major consequences for
funding, recruitment, and continued success of a university.

As an aside, you will see another message in
the graph – starting a faculty position is often coincident with a big drop in productivity.
For all you new profs out there worried about your slow start, take heart, it
is only temporary. It takes time to build up a lab and a research program – and
this is the case for EVERYONE.

Sabbaticals rule

In summary, sabbaticals are good for everyone
involved. Ok, fine, a politician might say, but “we don’t need to pay the full
salary – go out and get some yourself.” To those people, I would say: “Sabbaticals
when you travel are extremely expensive, particularly if you have a family.” If
you don’t provide full pay to professors, they are much less likely to go to
new places, which is of great benefit to many. (Of course, a great sabbatical
can also be had while staying in the same location.) My own university provides
full support for sabbatical every 7th year (or 6 months support
after every 3 years) – THANKS MCGILL – KEEP IT UP. However, even then, I lose
money. The only way I can make it work is because I can stay almost for free with
family in California and, most recently, the wonderful Miller Institute for
Basic Research helped fund my sabbatical at UC Berkeley.

So, please everyone, from someone who has now
had two sabbaticals, keep full support for sabbaticals every 7th
year. Everyone wins – except those countries, states, and universities who don’t
have them.

---------------------------------

To be honest, some graduate students might not benefit so much from their professor going away on sabbatical. Physical proximity between a professor and his/her students is more conducive than is skype to progress on their thesis. Of course, skype, joint field work, and visits can help minimize the cost to these students. Personally, I need to be better in this area on my next sabbatical.

Friday, February 3, 2017

Some might think it would be empowering to earn the moniker of "world's greatest evolutionary force" where it would seem some superhero can, Superman style, rapidly make something "evolve". Like tossing a common ancestor into a phone booth and out pops all the species of Darwin's Finches. Whelp, the reality is that this might not be such a great thing. What if this greatest evolutionary force might be causing detrimental things to happen such as biodiversity loss? What if this greatest evolutionary force is affecting human society?

Well, what might this greatest evolutionary force be? For better or for worse, it's humans. For most of us living in our privileged world with a roof over our heads and food in our stomach, it is easy to become ensconced in our little bubble of consumables and disposables while hiding behind some electronic device, and not think about how we, humans, are affecting evolutionary processes. For example, when something is domesticated for human consumption, be it crops or pets, what happens when those domesticated individuals intermix with wild individuals? What happens when we put antibiotics into the wild? What happens when we want to put taxidermy heads on our walls? What happens when we move something from one place to another, intentionally or by accident (does it matter?)? So, perhaps it's time to come out from behind your screen to think about these questions.

All of these questions are important, but it is not enough to just ask how we are influencing evolution, but to also ask what are the consequences of this? How is this feeding back on to humans and our societies? Well, in working with Andrew Hendry from McGill University and Erik Svensson from Lund University, we set out to agglomerate a special issue of Philosophical Transactions of the Royal Society - B focusing on just this question. We came up with the unimaginative, but descriptive title of "Human Influences on evolution, and the ecological and societal consequences".

We structured this issue in a slightly different way where we considered individual contexts of human influence as a 'topic'. These topics include things such as domestication, habitat fragmentation, hunting, urbanization, medicine, disease, and more. For most of the topics, we opted to have two manuscripts related to the topic: a review type article, focusing on a particular context, how that affects evolution, and then in turn, how this might affect humans, and an empirical paper that set out to test some of the ideas laid out in the review.

We considered everything within two theoretical frameworks. The first is the phenotypic adaptive landscape, where a three dimensional surface is pictured with the peaks representing high fitness phenotypes and the valleys representing low fitness phenotypes. Selection would then be acting to push a population up the adaptive peak. If that landscape is altered (say by humans introducing a novel predator), however, then the landscape, and thus selection will shift. Eco-evolutionary dynamics would then consider that change in a distribution of phenotypes and how that would affect the ecology of that population, including changes at the community and ecosystem level.

As you can imagine, trying to understand how everything is connected can be rather confusing, so we modified the "traditional" eco-evolutionary framework to incorporate all the different parts together.

Using this, we then set out to try and predict which human influence might have the strongest effects on evolutionary and ecological processes. By no means is what we've done comprehensive, it's merely a tiny stepping stone to fully comprehending the impacts that we humans are having on evolution and how that is feeding back to human society. One of the reasons making predictions is so difficult is because evolution can be influenced by a myriad of factors. For instance, predicting how invasive organisms will respond, as well as how the native populations will respond, are dependent on so many biotic and abiotic interactions, it's extremely difficult to predict if the invasion will succeed, and if so, what will the consequences of it be and then how that would subsequently affect human populations.

Let's take a look at one of our thoughts about human influences on evolutionary processes. Depending on the context, specific components can affect selection itself, or other components of evolution such as standing genetic variation or as we put it, evolutionary potential. In some contexts, a strong effect is quite obvious - hunting and harvesting are usually size specific, which will result in evolutionary changes in size. However, the hunting can not persist forever at high rates as the population would eventually go extinct. Perhaps more important is our efforts to control for pests or perceived "enemies" because it will result in increased tolerance and resistance, which then means we need stronger/better ways to control the enemies, and then they will again evolve increased tolerance. This perpetual "arms race" could, and has, led to things like superbugs that cannot be controlled with any current medicine.

What about potential ecological consequences as a result of this human induced evolutionary change? If we again consider hunting and harvesting, perhaps we are reducing the population size of or even removing a keystone species. If certain species are targeted, where individuals have a strong role in the community structure, their removal will have obvious cascading effects. For example, otters are essential in maintaining the giant kelp ecosystem in the Pacific Ocean, and the loss of otters in this ecosystem, perhaps due to pollution, then cascades into human society as important fisheries and a carbon sequestration source are subsequently lost.

I just wanted an excuse to post a photo of cute otters.

In our introductory article, we actually ask a total of eight questions relating to human influences on evolution and the consequences they have on human society. We know you will have opinion and agree or disagree with us, so we would love to hear from you in the comments. In a nutshell, we hope this issue make you realize just how much humans are influencing evolution, and that these human induced shifts in evolution have societal consequences. Unfortunately, a large number of those consequences are detrimental to humans. And we're not alone on this planet, so those negative consequences are also affecting everything else!!